There are numerous different types of catheter which are used for a multitude of medical purposes many of which involve the insertion of the catheter into a patient's body via, for example, an artery of the patient.
An example of such use is disclosed in our earlier U.S. Pat. Nos. 5,081,993 and 5,257,629. In those earlier U.S. Patents there is disclosed a catheter which has at its distal tip (distal with respect to the operating surgeon) an ultra-sonic transducer array adapted to emit ultrasonic signals and to receive their echoes in order to provide an image of the interior of the human organ in question, e.g an artery which could be inside the patient's heart.
Apart from the system disclosed in these two earlier patent specifications and the associated catheters for use in those systems, there is also the well-known balloon type catheter which is used to carry out a so-called angioplasty. This operation involves the insertion of the balloon catheter into a patient's artery, typically through the patient's thigh, and then feeding the distal end of the catheter into the damaged artery which could be within the patient's heart. Typically the damage can consist of so-called plaque or a loose part of the inside wall of the artery, as it were, hanging down into the artery thus impeding blood flow.
In carrying out an angioplasty operation the surgeon will need to accurately locate the balloon distal tip of the catheter in exactly the right position within the artery in relation to the plaque or damaged wall. Furthermore, it may be necessary for the surgeon to withdraw the tip at least to some extent and then to reposition it in the affected area.
Considerable skill, and therefore room for error, is involved in this accurate positioning of the distal end of the catheter.
The present invention is concerned with providing means whereby the surgeon can more easily locate the distal tip of the catheter in the required position within the patient or reposition that tip in the required position.
It is normal, to provide the proximal end of the catheter (proximal with respect to the surgeon) with some kind of "handle" by which the surgeon can grip the catheter in order to push it into the patient's artery and to feed it so that the distal end arrives at the desired position. It is also known to provide a catheter with some mechanical means for indicating to the surgeon the distance that the catheter has been inserted into the patient. More specifically, it is known to employ a motorised drive to pull back the catheter by a prescribed amount.
The present invention is concerned with providing improved means for indicating to the surgeon the position of the catheter within the patient and in particular the position of the distal end of the cather which distal end carries some operative device, such as a balloon, whereby the surgeon is able to effect the required treatment or operation. The distal end of the catheter could be provided with other devices/arrangements than a balloon, these device/arrangements being of many known kinds.
There is disclosed in U.S. Pat. No. 4,867,173 a catheter having a central guide wire the tip of which can be made of a radio opaque material to facilitate location of the distal end of the guide wire.
There is disclosed in European Patent Application 0050606 a dispensing container for venous catheters which container is provided with an indicator by which as the catheter is inserted into a patient the length that has been inserted can be read off.